0000000000016727
AUTHOR
A. Bracco
Response of AGATA segmented HPGe detectors to gamma rays up to 15.1MeV
WOS: 000314826000009
The distribution of the rotational transition strength in warm nuclei studied through γ-ray correlations
Abstract The study of damping of rotational motion applying te rotational plane mapping (RPM) method is presented and discussed. The aim of this technique is to extract the distribution of the rotational transition strength from an analysis of the shape of the “central valley” of two- and three-dimensional γ-ray spectra. The method is applied to a triple γ-coincidence data set of 162,163Tm nuclei formed in 37Cl+130Te reactions. The rotational transition strength is obtained as a function of rotational frequency for selected regions of entry states, and the width is found to be rather constant and approximately equal to 80 keV. This value is significantly smaller than the value predicted the…
Isospin Character of Low-Lying Pygmy Dipole States inPb208via Inelastic Scattering ofO17Ions
The properties of pygmy dipole states in Pb-208 were investigated using the Pb-208(O-17, O-17'gamma) reaction at 340 MeV and measuring the gamma decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted gamma rays and of the scattered particles were measured. The results are compared with (gamma, gamma') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2(+) and 3(-) states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first t…
Spectroscopy of nuclei approaching the proton drip-line using a secondary-fragmentation technique with the RISING detector array
An experiment utilizing a double fragmentation reaction was performed to study isobaric analogue states in A similar to 50 nuclei approaching the proton drip-line. gamma-ray spectroscopy will be used to identify excited states in the neutron-deficient nuclei produced in the second fragmentation reaction. Excited state level schemes will be obtained, through comparison with states in their well-known mirror partners, along with information on Coulomb effects through measurements of the Coulomb energy differences between isobaric analogue excited states. The validity of isospin symmetry for nuclei approaching the proton drip-line can also be investigated and the information gained will aid in…
Decay studies in the A∼225 Po-Fr region from the DESPEC campaign at GSI in 2021
The HISPEC-DESPEC collaboration aims at investigating the struc-ture of exotic nuclei formed in fragmentation reactions with decay spectroscopymeasurements, as part of the FAIR Phase-0 campaign at GSI. This paper reportson first results of an experiment performed in spring 2021, with a focus on beta-decaystudies in the Po-Fr nuclei in the 220 < A <230 island of octupole deformationexploiting the DESPEC setup. Ion-beta correlations and fast-timing techniques arebeing employed, giving an insight into this difficult-to-reach region. peerReviewed
The GALILEO γ-ray array at the Legnaro National Laboratories
Abstract GALILEO, a new 4 π high-resolution γ -detection array, based on HPGe detectors, has been developed and installed at the Legnaro National Laboratories. The GALILEO array greatly benefits from a fully-digital read-out chain, customized DAQ, and a variety of complementary detectors to improve the resolving power by the detection of particles, ions or high-energy γ -ray transitions. In this work, a full description of the array, including electronics and DAQ, is presented together with its complementary instrumentation.
Is Seniority a Partial Dynamic Symmetry in the First $\nu g_{9/2}$ Shell?
The low-lying structures of the midshell νg9/2 Ni isotopes 72Ni and 74Ni have been investigated at the RIBF facility in RIKEN within the EURICA collaboration. Previously unobserved low-lying states were accessed for the first time following β decay of the mother nuclei 72Co and 74Co. As a result, we provide a complete picture in terms of the seniority scheme up to the first (8+) levels for both nuclei. The experimental results are compared to shell-model calculations in order to define to what extent the seniority quantum number is preserved in the first neutron g9/2 shell. We find that the disappearance of the seniority isomerism in the (81+) states can be explained by a lowering of the se…
Isomers and high-spin structures in the N=81 isotones Xe135 and Ba137
The high-spin structures of the N = 81 isotones 135Xe and 137Ba are investigated after multinucleontransfer (MNT) and fusion-evaporation reactions. Both nuclei are populated in (i) 136Xe+238U and (ii) 136Xe+208Pb MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii), in the 136Xe+198Pt MNT reaction employing the -ray array GAMMASPHERE in combination with the gas detector array Chico, and (iv) via a 11B+130Te fusion-evaporation reaction. The high-spin level schemes of 135Xe and 137Ba are considerably extended to higher energies. The 2058-keV (19=2 ) state in 135Xe is identified as an isomer, completing the systema…
Interaction strength and shape difference for the h9/2 and h11/2 configurations in163Tm
The strongly shape driving πh9/2[541]l/2− configuration with α=+1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, ħωc, the aligned angular momentum, ix, and interaction strength, at the alignment of the first pair of i13/2 quasineutrons in several odd-Z rare earth-nuclei. The h9/2[541]1/2− and h11/2[523]7/2− bands have been studied in the stably deformed rare-earth nucleus163Tm to investigate these features. A difference in band crossing frequency of ∼ 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I=25/2–29/2 ħ. Theγ-decay pattern between the two bands is est…
Nuclear structure “southeast” ofPb208: Isomeric states inHg208andTl209
The nuclear structure of neutron-rich N>126 nuclei has been investigated following their production via relativistic projectile fragmentation of a E/A=1 GeV U-238 beam. Metastable states in the N=128 isotones Hg-208 and Tl-209 have been identified. Delayed gamma-ray transitions are interpreted as arising from the decay of I-pi=(8(+)) and (17/2(+)) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers Z 126.
Lifetime measurements in neutron-rich63,65Co isotopes using the AGATA demonstrator
Lifetimes of the low-lying (11/2-) states in 63,65Co have been measured employing the recoil distance doppler shift method (RDDS) with the AGATA γ-ray array and the PRISMA mass spectrometer. These nuclei were populated via a multinucleon transfer reaction by bombarding a 238U target with a beam of 64Ni. The experimental B(E2) reduced transition probabilities for 63,65Co are well reproduced by large-scale shell-model calculations that predict a constant trend of the B(E2) values up to the N=40 67Co isotope
Nature of seniority symmetry breaking in the semimagic nucleus $^{94}Ru$
Physical review / C 105(3), L031304 (2022). doi:10.1103/PhysRevC.105.L031304
Conceptual design and infrastructure for the installation of the first AGATA sub-array at LNL
WOS: 000295765100014
Evolution of deformation in neutron-rich Ba isotopes up to A=150
12 pags., 11 figs., 3 tabs. -- Open Access funded by Creative Commons Atribution Licence 4.0
'beta'-decay studies of neutron-rich 'TL', 'PB', and 'BI' isotopes
The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft fur Schwerionenforschung laboratory to investigate the β decay of neutron-rich nuclei just beyond 208Pb. This paper reports on β-delayed γ decays of 211-213Tl, 215Pb, and 215-219Bi de-exciting states in the daughters 211-213Pb, 215Bi, and 215-219Po. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden β transitions in this mass region is discussed. © 2014 American Physical Society.
Pygmy dipole resonance in 124Sn populated by inelastic scattering of 17O
L. Pellegri et al. ; 5 pags. ; 6 figs. ; open access article under the CC BY license. Funded by SCOAP3
Population of neutron-rich nuclei around 48ca with deep inelastic collisions
The deep inelastic reaction 48Ca+64Ni at 6 MeV/A has been studied using the CLARA–PRISMA setup. Angular distributions for pure elastic scattering and total cross-sections of the most relevant transfer channels have been measured. The experimental results are compared with predictions from a semiclassical model, showing good agreement for the presently analyzed few neutrons transfer channels. The decay of the most intense reaction products has also been studied, giving indications of the population of states with very short lifetimes. Gadea Raga, Andrés, Gadea.Andres@ific.uv.es
Low-lying excitations in Ni 72
A. I. Morales et al.; 14 págs.; 9 figs.; 3 tabs.
High-spin structures in Xe132 and Xe133 and evidence for isomers along the N=79 isotones
Author(s): Vogt, A; Siciliano, M; Birkenbach, B; Reiter, P; Hadynska-Klȩk, K; Wheldon, C; Valiente-Dobon, JJ; Teruya, E; Yoshinaga, N; Arnswald, K; Bazzacco, D; Blazhev, A; Bracco, A; Bruyneel, B; Chakrawarthy, RS; Chapman, R; Cline, D; Corradi, L; Crespi, FCL; Cromaz, M; De Angelis, G; Eberth, J; Fallon, P; Farnea, E; Fioretto, E; Fransen, C; Freeman, SJ; Fu, B; Gadea, A; Gelletly, W; Giaz, A; Gorgen, A; Gottardo, A; Hayes, AB; Hess, H; Hetzenegger, R; Hirsch, R; Hua, H; John, PR; Jolie, J; Jungclaus, A; Karayonchev, V; Kaya, L; Korten, W; Lee, IY; Leoni, S; Liang, X; Lunardi, S; MacChiavelli, AO; Menegazzo, R; Mengoni, D; Michelagnoli, C; Mijatovic, T; Montagnoli, G; Montanari, D; Muller-…
Isospin symmetry in thesdshell: Transition strengths in the neutron-deficientsdshell nucleusAr33
Reduced transition strengths of the deexciting transitions from the first two excited states in 33Ar were measured in a relativistic Coulomb excitation experiment at the GSI Helmholtz center. The radioactive ion beam was produced by fragmentation of a primary 36Ar beam on a 9Be target followed by the selection of the reaction product of interest via the GSI Fragment Separator. The 33Ar beam hit a secondary 197Au target with an energy of approximately 145 MeV/nucleon. An array of high-purity germanium cluster detectors and large-volume BaF2 scintillator detectors were employed for γ -ray spectroscopy at the secondary target position. The Lund-York-Cologne Calorimeter was used to track the ou…
Conceptual design of the AGATA 1$\pi$ array at GANIL
The Advanced GAmma Tracking Array (AGATA) has been installed at the GANIL facility, Caen-France. This setup exploits the stable and radioactive heavy-ions beams delivered by the cyclotron accelerator complex of GANIL. Additionally, it benefits from a large palette of ancillary detectors and spectrometers to address in-beam γ-ray spectroscopy of exotic nuclei. The set-up has been designed to couple AGATA with a magnetic spectrometer, charged-particle and neutron detectors, scintillators for the detection of high-energy γ rays and other devices such as a plunger to measure nuclear lifetimes. In this paper, the design and the mechanical characteristics of the set-up are described. Based on sim…
Resolution, efficiency and stability of HPGe detector operating in a magnetic field at various gamma-ray energies
Abstract The use of High Purity Germanium detectors (HPGe) has been planned in some future experiments of hadronic physics. The crystals will be located close to large spectrometers where the magnetic fringing field will not be negligible and their performances might change. Moreover high precision is required in these experiments. The contribution of magnetic field presence and long term measurements is unique. In this paper the results of systematic measurements of the resolution, stability and efficiency of a crystal operating inside a magnetic field of 0.8 T, using radioactive sources in the energy range from 0.08 to 1.33 MeV, are reported. The measurements have been repeated during sev…
Carbon monoxide improves cardiac energetics and safeguards the heart during reperfusion after cardiopulmonary bypass in pigs
Ischemia-reperfusion injury, a clinical problem during cardiac surgery, involves worsened adenosine trisphosphate (ATP) generation and damage to the heart. We studied carbon monoxide ( CO) pretreatment, proven valuable in rodents but not previously tested in large animals, for its effects on pig hearts subjected to cardiopulmonary bypass with cardioplegic arrest. Hearts of CO-treated pigs showed significantly higher ATP and phosphocreatine levels, less interstitial edema, and apoptosis of cardiomyocytes and required fewer defibrillations after bypass. We conclude that treatment with CO improves the energy status, prevents edema formation and apoptosis, and facilitates recovery in a clinical…
β decay studies of n-rich Cs isotopes with the ISOLDE Decay Station
R. Lica et al. -- 14 pags., 7 figs., tab. -- Open Access funded by Creative Commons Atribution Licence 3.0
Study of the γ decay of high-lying states in 208Pb via inelastic scattering of 17O ions
A measurement of the high-lying states in 208Pb has been made using 17O beams at 20 MeV/u. The gamma decay following inelastic excitation was measured with the detector system AGATA Demonstrator based on segmented HPGe detectors, coupled to an array of large volume LaBr3:Ce scintillators and to an array of Si detectors. Preliminary results in comparison with (γ,γ’) data, for states in the 5-8 MeV energy interval, are presented.
Fission and Quasi-Fission Dynamics Near the Coulomb Barrier: $\gamma$ Rays as Probe for their Timescale
International audience; The overlap in the mass symmetric region of the reaction products from fusion-fission and quasi-fission complicates the assignment of symmetric events to complete fusion on the basis of the mass distribution alone. Additional observables, besides mass distribution, should be used. The method proposed here relies on the fact that fusion-fission and quasifission are characterized by a different timescale. Within this framework we performed a detailed study to find out if timescales can be probed via angular momentum as measured via γ rays multiplicity. The proof of principle was carried out by measuring the γ rays in coincidence with two fragments in the reaction 32S +…
Hindered Gamow-Teller Decay to the Odd-OddN=ZGa62: Absence of Proton-NeutronT=0Condensate inA=62
Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, Jπ=0+ ground state of Ge62 into excited states of the odd-odd N=Z nucleus Ga62. The experiment is performed at GSI Helmholtzzentrum fur Schwerionenforschung with the Ge62 ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14) ms is measured for the Ge62 ground state. Six excited states of Ga62, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical pred…
Isospin dependence of electromagnetic transition strengths among an isobaric triplet
*Aydın, Sezgin ( Aksaray, Yazar )
Angular momentum population in fragmentation reactions
Neutron-deficient nuclei with N = 126 have been populated following projectile fragmentation of a 238U beam with energy 1 GeV/A. The decay of several previously reported isomers has been measured. This will allow us to calculate high-spin isomeric ratios and compare them with model calculations to allow a better understanding of the reaction mechanism. Algora, Alejandro, Alejandro.Algora@ific.uv.es ; Molina Palacios, Francisco Manuel, Francisco.Molina@ific.uv.es ; Rubio Barroso, Berta, Berta.Rubio@ific.uv.es
Structure of N >= 126 nuclei produced in fragmentation of (238)U
The nuclear structure of neutron‐rich N⩾126 nuclei have been investigated following their production via relativistic projectile fragmentation of a E/A = 1 GeV 238U beam on a Be target. The cocktail of secondary beam products were separated and identified using the GSI FRagment Separator (FRS). The nuclei of interest were implanted in a high‐granularity active stopper detector set‐up consisting of 6 double sided silicon strip detectors. The associated gamma‐ray transitions were detected with the RISING array, consisting of 15 Euroball cluster Ge‐detectors. Time‐correlated gamma decays from individually identified nuclear species have been recorded, allowing the clean identification of isome…
Probing the nature of particle–core couplings in 49Ca with γ spectroscopy and heavy-ion transfer reactions
Neutron rich nuclei around 48Ca have been measured with the CLARA–PRISMA setup, making use of 48Ca on 64Ni binary reactions, at 5.9 MeV/A. Angular distributions of γ rays give evidence, in several transfer channels, for a large spin alignment (≈70%) perpendicular to the reaction plane, making it possible to firmly establish spin and parities of the excited states. In the case of 49Ca, states arising from different types of particle–core couplings are, for the first time, unambiguously identified on basis of angular distribution, polarization and lifetime measurements. Shell model and particle–vibration coupling calculations are used to pin down the nature of the states. Evidence is found fo…
Fast-timing Measurement in \(^{96}\)Pd: Improved Accuracy for the Lifetime of the \(4_1^{+}\) State
Direct lifetime measurements via γ–γ coincidences using the FATIMA fast-timing LaBr3(Ce) array were performed for the excited states below previously reported isomers. In the N = 50 semi-magic 96Pd nucleus, lifetimes below the I π = 8+ seniority isomer were addressed as a benchmark for further analysis. The results for the I π = 2+ and 4 + states confirm the published values. Increased accuracy for the lifetime value was achieved for the 4 + state. peerReviewed
Isomeric decay spectroscopy of theBi217isotope
The structure of the neutron-rich bismuth isotope 217Bi has been studied for the first time. The fragmentation of a primary 238U beam at the FRS-RISING setup at GSI was exploited to perform γ-decay spectroscopy, since μs isomeric states were expected in this nucleus. Gamma rays following the decay of a t1/2=3 μs isomer were observed, allowing one to establish the low-lying structure of 217Bi. The level energies and the reduced electric quadrupole transition probability B(E2) from the isomeric state are compared to large-scale shell-model calculations.
New μs Isomers in the Neutron-rich 210Hg Nucleus
Neutron-rich nuclei in the lead region, beyond N = 126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in Hg-210: the 8(+) isomer expected from the seniority scheme in the vg(9/2) shell and a second one at low spin and low excitation energy. The decay strength of the 8(+) isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3(-) state, although this is in contrast with theoretical expectations. (C) 2013 Elsevier B.V. All rights reserved.
Reaction dynamics and nuclear structure studies via deep inelastic collisions with heavy-ions: spin and parity assignment in49Ca
The population and gamma decay of neutron rich nuclei around 48Ca has been measured at Legnaro National Laboratory with the PRISMA-CLARA setup, using deep-inelastic collisions (DIC) on 64Ni, at an energy approximately twice the Coulomb barrier. The reaction properties of the main products are investigated, focusing on total cross sections and angular distributions both integrated in energy and associated to the population of specific excited states. Gamma spectroscopy studies are also performed, giving evidence, for the first time in transfer reactions with heavy ions, of a large spin alignment (~70%), perpendicular to the reaction plane. This makes possible the use of angular distributions…
Gamma rays as probe of fission and quasi-fission dynamics in the reaction 32S + 197Au near the Coulomb barrier
International audience; Compound nucleus fission and quasi-fission are both binary decay channels whose common properties make the experimental separation between them difficult. A way to achieve this separation could be to probe the angular momentum of the binary fragments. This can be done detecting gamma rays in coincidence with the two fragments. As a case study, the reaction 32S + 197Au near the Coulomb barrier has been performed at the Tandem ALTO facility at IPN ORSAY. ORGAM and PARIS, two different gamma detectors arrays, are coupled with the CORSET detector, a two-arm time-of-flight spectrometer. TOF-TOF data were analyzed to reconstruct the mass-energy distribution of the primary …
High-spin structure of Xe134
A. Vogt et al. ; 12 págs.; 9 figs.; 1 tab.
In-beam γ -ray spectroscopy of the neutron-rich platinum isotope Pt200 toward the N=126 shell gap
The neutron-rich nucleus \nucleus{200}{Pt} is investigated via in-beam \gamma-ray spectroscopy in order to study the shape evolution in the neutron-rich platinum isotopes towards the N = 126 shell closure. The two-neutron transfer reaction \nucleus{198}{Pt}(\nucleus{82}{Se}, \nucleus{80}{Se})\nucleus{200}{Pt} is used to populate excited states of \nucleus{200}{Pt}. The Advanced Gamma Ray Tracking Array (AGATA) demonstrator coupled with the PRISMA spectrometer detects \gamma rays coincident with the \nucleus{80}{Se} recoils, the binary partner of \nucleus{200}{Pt}. The binary partner method is applied to extract the \gamma-ray transitions and build the level scheme of \nucleus{200}{Pt}. The …
Experimental program of the Super-FRS Collaboration at FAIR and developments of related instrumentation
The physics program at the super-conducting fragment separator (Super-FRS) at FAIR, being operated in a multiple-stage, high-resolution spectrometer mode, is discussed. The Super-FRS will produce, separate and transport radioactive beams at high energies up to 1.5 AGeV, and it can be also used as a stand-alone experimental device together with ancillary detectors. Various combinations of the magnetic sections of the Super-FRS can be operated in dispersive, achromatic or dispersion-matched spectrometer ion-optical modes, which allow measurements of momentum distributions of secondary-reaction products with high resolution and precision. A number of unique experiments in atomic, nuclear and h…
Low-lying electric dipole gamma-continuum for the unstable Fe-62,64 nuclei : Strength evolution with neutron number
6 pags., 4 figs.
Evidence of Partial Seniority Conservation in the pi g9/2 Shell for the N=50 Isotones
The reduced transition probabilities for the 4-> and 2->0 transitions in 92Mo and 94Ru and for the 4->2 and 6->4 transitions in 90Zr have been determined in this experiment making use of a multinucleon transfer reaction. These results have been interpreted on the basis of realistic shell-model calculations in the f5/2, p3/2, p1/2, and g9/2 proton valence space. Only the combination of extensive lifetime information and large scale shell-model calculations allowed the extent of the seniority conservation in the N=50 g9/2 orbital to be understood. The conclusion is that seniority is largely conserved in the first πg9/2 orbital.
Cluster-transfer reactions with radioactive beams: A spectroscopic tool for neutron-rich nuclei
An exploratory experiment performed at REX-ISOLDE to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The reactions Li7(Rb98,αxn) and Li7(Rb98,txn) were studied through particle-γ coincidence measurements, and the results are presented in terms of the observed excitation energies and spins. Moreover, the reaction mechanism is qualitatively discussed as a transfer of a clusterlike particle within a distorted-wave Born approximation framework. The results indicate that cl…
Shape isomerism and shape coexistence effects on the Coulomb energy differences in theN=Znucleus66As and neighboringT=1multiplets
Excited states of the $N=Z=33$ nucleus ${}^{66}$As have been populated in a fusion-evaporation reaction and studied using $\ensuremath{\gamma}$-ray spectroscopic techniques. Special emphasis was put into the search for candidates for the $T=1$ states. A new 3${}^{+}$ isomer has been observed with a lifetime of 1.1(3) ns. This is believed to be the predicted oblate shape isomer. The excited levels are discussed in terms of the shell model and of the complex excited Vampir approaches. Coulomb energy differences are determined from the comparison of the $T=1$ states with their analog partners. The unusual behavior of the Coulomb energy differences in the $A=70$ mass region is explained through…
High-spin structure in the transitional nucleus Xe131 : Competitive neutron and proton alignment in the vicinity of the N=82 shell closure
The transitional nucleus 131Xe is investigated after multinucleon transfer (MNT) in the 136Xe+208Pb and 136Xe+238U reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy and as an elusive reaction product in the fusion-evaporation reaction 124Sn(11B,p3n) 131Xe employing the HORUS γ-ray array coupled to a double-sided silicon strip detector (DSSSD) at the University of Cologne, Germany. The level scheme of 131Xe is extended to 5 MeV. A pronounced backbending is observed at ~ω ≈ 0.4 MeV along the negative-parity one-quasiparticle νh11/2(α = −1/2) band. The results are compared to t…
AGATA-Advanced GAmma Tracking Array
WOS: 000300864200005